Oxidation catalyst monitoring

ABSTRACT

A control method for monitoring an oxidation catalyst of an exhaust system is provided. The control method includes determining an open loop factor based on an aging factor and an efficiency curve; controlling an injection of hydrocarbons into an exhaust stream based on the open loop factor; and monitoring the oxidation catalyst based on the injection of hydrocarbons.

FIELD OF THE INVENTION

The subject invention relates to methods, and systems for monitoring an oxidation catalyst of an exhaust system.

BACKGROUND

An oxidation catalyst device is provided in an exhaust system to treat unburned gaseous and non-volatile hydrocarbon (HC) and carbon monoxide (CO). The oxidation catalyst oxidizes the HC and CO under high temperatures conditions to form carbon dioxide (CO₂) and water (H₂O). As the oxidation catalyst ages, its ability to oxidize the HC and CO is affected. Accordingly, it is desirable to provide methods and systems that monitor the operation of the oxidation catalyst.

SUMMARY OF THE INVENTION

In one exemplary embodiment, a control method for monitoring an oxidation catalyst is provided. The control method includes: determining an open loop factor based on an aging factor and an efficiency curve; controlling an injection of hydrocarbons into an exhaust stream based on the open loop factor; and monitoring the oxidation catalyst based on the injection of hydrocarbons.

In another exemplary embodiment, a control system for monitoring an oxidation catalyst of an exhaust system is provided. The control system includes a first module that determines an open loop factor based on an aging factor and an efficiency curve. A second module controls an injection of hydrocarbons into an exhaust stream based on the open loop factor. A third module monitors the oxidation catalyst based on the injection of hydrocarbons.

In yet another exemplary embodiment, an exhaust system of an engine is provided. The exhaust system includes an oxidation catalyst, and a control module. The control module determines an open loop factor based on an aging factor and an efficiency curve, injects hydrocarbons into an exhaust stream based on the open loop factor, and monitors the oxidation catalyst based on the injection of hydrocarbons.

The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which:

FIG. 1 is a functional block diagram of a vehicle including an engine and exhaust system in accordance with exemplary embodiments;

FIG. 2 is a dataflow diagram of an exhaust system control system in accordance with exemplary embodiments; and

FIG. 3 is a flowchart illustrating an exhaust system control method in accordance with exemplary embodiments.

DESCRIPTION OF THE EMBODIMENTS

The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

Referring now to FIG. 1, an exemplary embodiment is directed to a vehicle 10 that includes an exhaust treatment system 12 for the reduction of regulated exhaust gas constituents of an internal combustion engine 14. As can be appreciated, the exhaust treatment system 12 described herein can be implemented in various engine systems. Such engine systems may include, for example, but are not limited to, diesel engine systems, gasoline engine systems, and homogeneous charge compression ignition engine systems.

As shown in FIG. 1, the exhaust treatment system 12 generally includes one or more exhaust gas conduits 16, and one or more exhaust treatment devices. The exhaust treatment devices may include an oxidation catalyst device (OC) 18. In the example of FIG. 1, the exhaust treatment devices further include a selective catalytic reduction device (SCR) 20 and a particulate filter (PF) 22. As can be appreciated, the exhaust treatment system 12 of the present disclosure may include various combinations of the OC 18 and other exhaust treatment devices and is not limited to the present example.

In FIG. 1, the exhaust gas conduit 16, which may comprise several segments, transports exhaust gas 24 from the engine 14 to the exhaust treatment devices of the exhaust treatment system 12. The OC 18 may include, for example, a flow-through metal or ceramic monolith substrate. The substrate may be packaged in a shell or canister having an inlet and an outlet in fluid communication with the exhaust gas conduit 16. The substrate may include an oxidation catalyst compound disposed thereon. The oxidation catalyst compound may be applied as a wash coat and may contain platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh) or other suitable oxidizing catalysts, or combination thereof. The OC 18 treats unburned gaseous and non-volatile HC and CO, which are oxidized to form CO₂ and H₂O.

A control module 32 controls the engine 14 and one or more components of the exhaust treatment system 12 based on sensed and/or modeled data. For example, one or more sensors 34 sense a temperature of the exhaust gas 24 at various locations in the exhaust system 12 and generates a sensor signal based thereon. The control module 32 receives the signal and monitors the operation of the OC 18 based on the signal and the OC monitoring systems and methods of the present disclosure.

In various embodiments, the control module 32 adjusts a level of HC (e.g. excess fuel) present in the exhaust gas by, controlling an injection of fuel into the exhaust gas (e.g., into the cylinder or the exhaust conduit). The control module 32 adjusts the level based on an aging factor and an efficiency factor. The control module 32 monitors the operation of the OC 18 based on the adjusted HC injection and sets a diagnostic code based on the monitoring. The control module 32 can further report the diagnostic code according to various reporting methods, including, but not limited to, using in-vehicle communication reporting messages and/or off-vehicle reporting messages.

Referring now to FIG. 2, and with continued reference to FIG. 1, a dataflow diagram illustrates various embodiments of an exhaust system control system that may be embedded within the control module 32. Various embodiments of exhaust system control systems according to the present disclosure may include any number of sub-modules embedded within the control module 32. As can be appreciated, the sub-modules shown in FIG. 2 may be combined and/or further partitioned to similarly monitor the operation of the OC 18 (FIG. 1). Inputs to the system may be sensed from the exhaust system 12, received from other control modules (not shown), and/or determined/modeled by other sub-modules (not shown) within the control module 32. In various embodiments, the control module 32 includes a factor determination module 40, an HC control module 42, and an evaluation module 44.

The factor determination module 40 receives as input an aging factor 46 and an efficiency curve 48. The aging factor 46 is a value that indicates an age of the OC 18 (FIG. 1). For example, the aging factor 46 can be based on miles driven, hours of operation of the engine 14 (FIG. 1), or any other time based value. The efficiency curve 48 is a set of data indicating predicted efficiencies of the OC 18 (FIG. 1) at various ages. The efficiency curve 48, for example, can be determined from exhaust system parameters or can be predefined based on physical characteristics of the OC 18 (FIG. 1).

Based on the aging factor 46 and the efficiency curve 48, the factor determination module 40 determines an open loop factor 50. In various embodiments, the open loop factor 50 can be between, for example, one and two, and can be retrieved from a lookup table that is indexed by the efficiency curve 48 and the aging factor 46.

The HC control module 42 receives as input the open loop factor 50. Based on the open loop factor 50, the HC control module 42 generates control signals 52 to the engine 14 (FIG. 1) and/or the exhaust system 12 (FIG. 1) to control a level of hydrocarbon in the exhaust gas 24 (FIG. 1). For example, the open loop factor 50 may be multiplied by a determined HC quantity 54 to determine an adjusted HC quantity 56. The control signals 54 are generated to the engine 14 (FIG. 1) and/or the exhaust system 12 (FIG. 1) based on the adjusted HC quantity 56.

The reporting module 44 receives as input sensor signals 58 indicating a temperature of the exhaust gas 24 (FIG. 1) downstream of the OC 18 (FIG. 1). The reporting module 44 evaluates the sensor signals 58 based on the adjusted HC quantity 56 to determine if the actual temperature has reached an expected temperature. If the actual temperature is equal to or within a range of the expected temperature, then the OC 18 (FIG. 1) is diagnosed as being operational and a fault status or diagnostic code is set to indicate no fault. If, however the actual temperature is outside of the range of the expected temperature, then the OC 18 (FIG. 1) is diagnosed as being faulty and a fault status or diagnostic code is set to indicate a fault.

The reporting module 44 may then report the fault status or diagnostic code via a message 60. In various embodiments, the reporting module 44 generates the message 60 on a serial data bus (not shown) of the vehicle 10 (FIG. 1), where the message can be transmitted to a remote location using a telematics system (not shown) of the vehicle 10 (FIG. 1) or can be retrieved by a technician tool (not shown) connected to the vehicle 10 (FIG. 1).

Referring now to FIG. 3, and with continued reference to FIGS. 1 and 2, a flowchart illustrates an exhaust system control method that can be performed by the control module 32 of FIG. 1 in accordance with the present disclosure. As can be appreciated in light of the disclosure, the order of operation within the method is not limited to the sequential execution as illustrated in FIG. 3, but may be performed in one or more varying orders as applicable and in accordance with the present disclosure.

In various embodiments, the method can be scheduled to run based on predetermined events, and/or run continually during operation of the engine 14.

In one example, the method may begin at 100. The aging factor 46 is determined at 100. The efficiency curve 48 is determined at 110. The open loop factor 50 is determined from the aging factor 46 and the efficiency curve 48 at 120. The adjusted HC amount 56 is determined based on the open loop factor 46 at 130. The control signals 52 are generated to achieve the adjusted HC amount 56 at 140.

The sensor signals 58 are evaluated at 150. If the sensor signals 58 indicate the exhaust temperature is within a range at 150, then the fault status is set to indicate no fault at 160 and the message 60 is generated that includes the fault status at 170. If, however, the sensor signals 58 indicate that the exhaust temperature is outside of a range at 150, then the fault status is set to indicate a fault at 180 and the message 60 is generated that includes the fault status at 170. The method may end at 190.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the application. 

What is claimed is:
 1. A control method for monitoring an oxidation catalyst of an exhaust system, comprising: determining an open loop factor based on an aging factor and an efficiency curve; controlling an injection of hydrocarbons into an exhaust stream based on the open loop factor; and monitoring the oxidation catalyst based on the injection of hydrocarbons.
 2. The control method of claim 1, wherein the aging factor is determined based on at least one of miles driven, and a time of operation.
 3. The control method of claim 1, wherein the efficiency curve is predefined based on physical characteristics of the oxidation catalyst.
 4. The control method of claim 1, wherein the efficiency curve is determined based on sensed parameters of the exhaust system.
 5. The control method of claim 1, wherein the monitoring the oxidation catalyst comprises monitoring a temperature of exhaust gas exiting the oxidation catalyst.
 6. The control method of claim 5, further comprising generating a message based on the monitoring.
 7. A control system for monitoring an oxidation catalyst of an exhaust system, comprising: a first module that determines an open loop factor based on an aging factor and an efficiency curve; a second module that controls injection of hydrocarbons into an exhaust stream based on the open loop factor; and a third module that monitors the oxidation catalyst based on the injection of hydrocarbons.
 8. The control system of claim 7, wherein the aging factor is determined based on at least one of miles driven, and a time of operation.
 9. The control system of claim 7, wherein the efficiency curve is predefined based on physical characteristics of the oxidation catalyst.
 10. The control system of claim 7, wherein the efficiency curve is determined based on sensed parameters of the exhaust system.
 11. The control system of claim 7, wherein the third module monitors the oxidation catalyst based on a temperature of exhaust gas exiting the oxidation catalyst.
 12. The control system of claim 11, wherein the third module generates a message based on the monitoring.
 13. An exhaust system of an engine, comprising: an oxidation catalyst; and a control module that determines an open loop factor based on an aging factor and an efficiency curve, that injects hydrocarbons into an exhaust stream based on the open loop factor, and that monitors the oxidation catalyst based on the injection of hydrocarbons.
 14. The exhaust system of claim 13, wherein the aging factor is determined based on at least one of miles driven, and a time of operation.
 15. The exhaust system of claim 13, wherein the efficiency curve is predefined based on physical characteristics of the oxidation catalyst.
 16. The exhaust system of claim 13, wherein the efficiency curve is determined based on sensed parameters of the exhaust system.
 17. The exhaust system of claim 13, wherein the control module monitors the oxidation catalyst based on a temperature of exhaust gas exiting the oxidation catalyst. 